[jira] [Updated] (HBASE-8806) Row locks are acquired repeatedly in HRegion.doMiniBatchMutation for duplicate rows.

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-8806?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lars Hofhansl updated HBASE-8806:
---------------------------------

    Priority: Critical  (was: Major)

I am marking this critical, because in some scenarios this could render replication useless (if the same rows are updated frequently, for example as counters).

Patch looks good. A minor nit is that we need to create the HashBytes in two places now.

As a general question: Should we introduce reentrant locks? If requested we could keep track of the current thread's id, and if the same thread requests a lock on the same row again, we'd return the current lock. This would be optional, maybe via a new flag to getLock. Cleanup might be a bit tricky in that case.

I'm happy with approach in this patch as well.
                
> Row locks are acquired repeatedly in HRegion.doMiniBatchMutation for duplicate rows.
> ------------------------------------------------------------------------------------
>
>                 Key: HBASE-8806
>                 URL: https://issues.apache.org/jira/browse/HBASE-8806
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver
>    Affects Versions: 0.94.5
>            Reporter: rahul gidwani
>            Priority: Critical
>             Fix For: 0.95.2, 0.94.10
>
>         Attachments: HBASE-8806-0.94.10.patch, HBASE-8806-0.94.10-v2.patch
>
>
> If we already have the lock in the doMiniBatchMutation we don't need to re-acquire it. The solution would be to keep a cache of the rowKeys already locked for a miniBatchMutation and If we already have the 
> rowKey in the cache, we don't repeatedly try and acquire the lock.  A fix to this problem would be to keep a set of rows we already locked and not try to acquire the lock for these rows.  
> We have tested this fix in our production environment and has improved replication performance quite a bit.  We saw a replication batch go from 3+ minutes to less than 10 seconds for batches with duplicate row keys.
> {code}
> static final int ACQUIRE_LOCK_COUNT = 0;
>   @Test
>   public void testRedundantRowKeys() throws Exception {
>     final int batchSize = 100000;
>     
>     String tableName = getClass().getSimpleName();
>     Configuration conf = HBaseConfiguration.create();
>     conf.setClass(HConstants.REGION_IMPL, MockHRegion.class, HeapSize.class);
>     MockHRegion region = (MockHRegion) TestHRegion.initHRegion(Bytes.toBytes(tableName), tableName, conf, Bytes.toBytes("a"));
>     List<Pair<Mutation, Integer>> someBatch = Lists.newArrayList();
>     int i = 0;
>     while (i < batchSize) {
>       if (i % 2 == 0) {
>         someBatch.add(new Pair<Mutation, Integer>(new Put(Bytes.toBytes(0)), null));
>       } else {
>         someBatch.add(new Pair<Mutation, Integer>(new Put(Bytes.toBytes(1)), null));
>       }
>       i++;
>     }
>     long startTime = System.currentTimeMillis();
>     region.batchMutate(someBatch.toArray(new Pair[0]));
>     long endTime = System.currentTimeMillis();
>     long duration = endTime - startTime;
>     System.out.println("duration: " + duration + " ms");
>     assertEquals(2, ACQUIRE_LOCK_COUNT);
>   }
>   @Override
>   public Integer getLock(Integer lockid, byte[] row, boolean waitForLock) throws IOException {
>     ACQUIRE_LOCK_COUNT++;
>     return super.getLock(lockid, row, waitForLock);
>   }
> {code}

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